EP 0616886 discloses a printing machine for printing on cardboard sheets intended to form containers. The converting machine comprises converting members, in particular a plate cylinder and an anilox cylinder, for inducing a conversion of each cardboard sheet, in this case printing by ink deposition. The plate cylinder and anilox cylinder operate according to adjustable parameters; in particular, their axes can be moved by motors. In addition, the converting machine comprises a graphical interface, a control keyboard for entering commands, and a processing unit.
According to the control method of the converting machine, the operator must enter a plurality of distinct commands for acting on a plurality of adjustable parameters that influence the same conversion.
However, the converting machine operates with many adjustable parameters, typically forty, including the three directions of movement, in both directions, of each converting member, which can influence the same conversion independently.
For example, for adjusting the contrast of a color on each plate element, the operator can choose to adjust eleven parameters independently, in an increasing direction or in a decreasing direction, i.e. twenty-two possible adjustments:                the spatial position of the plate cylinder according to three axes;        the spatial position of the anilox cylinder according to three axes;        the spatial position of the counter-pressure member according to three axes;        the rotation speed of the plate cylinder, and/or        the rotation speed of the anilox cylinder.        
For acting on these multiple adjustable parameters, the operator must enter a plurality of distinct commands successively. The operator must therefore necessarily know how each adjustable parameter influences the forthcoming conversion on the plate elements. In particular, the operator must necessarily anticipate the consequences of each of the adjustments thereof in an increasing direction or in a decreasing direction.
Consequently, it is long and tedious to implement a control method of the prior art for adjusting a converting machine of the prior art. Typically, the adjustment time for varying a conversion is generally longer than 10 minutes.
In addition, a control method of the prior art leads to a high risk of committing many adjustment errors, in particular in the case of an insufficiently experienced operator.